1. Field of the Invention
This patent application relates to the field of data transfer. More particularly, but not exclusively, it relates to a modem for data transfer, which is capable of modulating or demodulating data using multiple modulation techniques.
2. Description of the Related Art
In order to transmit information or data from one point to another or from one device to a second device, either via a communication line or a wireless link, data is transformed into a suitable form for being transmitted, typically by putting it onto a carrier. This is called modulation. After the data has been received by the second device, the modulated data is “demodulated”, i.e. removed from the carrier and brought back into a suitable form for future use by the second device.
More and more devices are designed to communicate with each other, for example via a local area network (LAN). For wireless LANs, different modulation standards have been introduced for ensuring compatibility such as the IEEE 802.11 standard. A similar concept for data transmission, but more commonly used for Personal Area Networking (PAN), can be seen in the Bluetooth™ standard.
Devices capable of communicating with other devices via a particular modulation technique each include a modulator and/or a demodulator, which is particularly designed for modulating/demodulating data according to the particular modulation technique. For example, referring now to FIG. 2, a modem 30 is illustrated, including a modulator 32 and a demodulator 34. The modulators and demodulators for different modulation techniques can differ considerably from each other.
If one particular device is designed to communicate using two different standards, for example the IEEE 802.11 and the Bluetooth standard, the approach adopted in the prior art is to use a combined modem including two separate modems, wherein each of these separate modems works according to one modulation technique. Such a modem is illustrated in FIG. 3.
Referring to FIG. 3, the modem 40 includes two separate modems 41 and 47. Modem 41 comprises modulator 42 and demodulator 44, whereas the modem 47 comprises modulator 43 and demodulator 45. The first modulator 42 and the first demodulator 44 are specific to the IEEE 802.11b technique and the second modulator 43 and the second demodulator 45 are specific to the Bluetooth standard. In addition to the two modems, an additional switching and interworking element 46 is required, which ensures that data is modulated according to the desired standard for a particular application and that incoming modulated data is correctly demodulated. The interworking element 46 also ensures that each modem pair is correctly updated with control information to ensure that any switching between modems has the correct timing alignment and that correct control procedures are carried out.
Accordingly, the present invention has been designed to improve the system described above.